An intensive, three-year feral cat eradication project on remote San Nicolas Island is complete, and has been deemed successful according to partners in conservation directly involved with the feline’s removal.
Located 61 miles off the Ventura County coastline, San Nicolas is the third-largest island off the California coast. The distant, windswept isle has been owned by the Navy since 1933, and is prime haul-out and pupping habitat for large rookeries of northern elephant seals and California sea lions.
Feral cat control has been a long-term endeavor. The island has a long history of feral populations, including goats and dogs. The cats were the last of the feral populations to go. Over time they’ve had a negative impact on land and seabird populations and island night lizards. They also were in direct competition with endemic island foxes, a federally protected species.
The Montrose Settlements Trustee Council contributed $3 million to the project, working jointly with the Navy, Island Conservation, the Institute for Wildlife Studies and the Humane Society of the United States.
“The cats were utilizing the entire island, from coast to coast, and the interior plateaus,” said Chad Hanson, project manager for Island Conservation. “They were particularly active during nesting season.”
Over the years the nests of western snowy plovers, Brandt’s cormorants, western gulls, black oystercatchers and horned larks have been easy targets for feral cats. They also preyed on sluggish island night lizards, and competed with island foxes over similar prey items and denning sites. The threat of rabies and other diseases being spread to island foxes was also a concern.
After five years of project planning from 2004 to 2008, and completion of the final environmental assessment in May 2009, Island Conservation and IWS began using camera traps across the 14,562-acre island that June. From there they implemented padded leg-hold live traps. The feral cats were trapped then transported off the island to a rehabilitation facility designed by the Humane Society in Ramona in San Diego County.
More than 70 islands around the world have successfully removed feral cat populations. However, San Nicolas is the largest island in the world for successful cat eradication without the use of a toxicant to date, and the largest island in the United States to complete a cat eradication project so far.
“Feral cats proved to be more ravenous, more aggressive than island foxes,” said Dave Garcelon, president of IWS, who has worked extensively in the recovery of California Channel Islands species for 30 years.
A makeshift hospital was built on the island in case any cats or island foxes were injured during trappings. Island foxes are similar in size to feral cats and were accidentally trapped. A total of 1,011 fox captures took place during the feral cat eradication project.
“Feral cats aren’t much different than bobcats,” Garcelon said. “They weren’t real happy about being in captivity.”
Cats most likely were brought to the island as pets and for pest control in the early 1900s, during the island’s ranching era. By the 1950s, large numbers of feral cats were roaming the 9-mile-long, 3.5-mile-wide island.
By the time Island Conservation and IWS finished trapping duties, they had removed 66 cats. Ten kittens were transferred off the island and adopted. The other cats are being rehabilitated and in time will be up for adoption. The last cat detected and removed was in June 2010, but monitoring continued until December 2011.
“They were very feral,” said Kim D’amico, a wildlife care specialist for the Humane Society. “They’re become accustomed to humans and have grown more friendly. This is the first time we’ve done anything like this off an island.”